[en] Plant roots are dynamically evolving organs able to undergo morphological and physiological changes to overcome water and nutrient limitation. The availability of these resources in the soil environment is naturally heterogeneous and subject to fluctuations. These oscillations are expected to intensify under climate change and increased drought stress. In these circumstances, it is crucial to understand how dynamic roots are in modifying their properties in order to rapidly chase and acquire water and nutrients. Short-scale dynamic adjustments are also often overlooked but can be important for plant fitness and can strongly affect carbon fluxes between the above and below-ground.
In the first chapter of this thesis I documented rapid shifts in root distribution in response to localized, short-term water injections in a lab experiment. In Chapter 2 I followed up on Chapter 1 and observed root distribution adjustments both at the seasonal scale and on a daily-basis following precipitation events in a minirhizotron study within a natural grassland. In Chapter 3 I detected a minute-scale increase in respiration rates and a decline in water uptake from roots exposed to pulses in ammonium concentrations in a split-root setup. Higher respiration rates might have been given by activation of proton pumps, facilitating the uptake of ammonium. The ammonium uptake could have then acidified the root environment and reduced aquaporin activity.
The results provide evidence that roots are highly dynamic structures, capable of locally changing their properties and growth rates within days, following sudden shifts in surrounding resource availability. My findings expand our knowledge on plant morphodynamics and could point to new ways towards more water and nutrient efficient agricultural practices. The observed mechanisms and adaptations could also be integrated in vegetation models to enhance their predictive capabilities.
